The Grey Council has had a presence in four of the six books since TC. They just haven't had time to express the covert stuff as the Grey Council. Whether it was the battles in Chichen Itza or Chicago or near Demonreach, they've had a presence in all the major fights. They missed GS and SG.

The thing is though, veils would have been a huge asset to his work as a PI. Being able to sneak into places or follow people undetected can only be pluses. Molly's abilities would make her a main protagonist in many other series. As a team they'd be very effective with Harry being the muscle and Molly the brains.

Do not underestimate Mab.  The only things we seen in in the Dresdenverse that top her are the Mothers, angels and Old Gods/Titans. I don't think Chauncey measures up to that level. Harry is often an idiot, but even he doesn't something he can't hope to control without a pressing reason.

Well, drawing from my knowledge of mythology and some speculation.

We've seen nothing from any Hindu, Chinese, Japanese, Polynesian, African, Australian or Middle Eastern Pantheons. Rakshasa have been mentioned but we have no Djinni. We have had the Loup Garou and Hexxenwolves but no traditional lycanthropes. Vadderung is our only active Legendary Hero but that will probably change in the wrestling book. The Amerind/Aleut pantheons probably should have had something in BG.

I'd guess the world will expand some in the coming books but there is a limit to how much the Wizard of Chicago will travel and to how much Jim wants to add.

I guess you can count Mouse and his brethren as part of an Asian contingent and we did have the bird people in Change.

Justin was being shielded, probably by Lea.  When Butcher rewrote canon for Morgan he explicitly says he couldn't find Harry by magical means which means he was looking.

Say rather that Harry was being shielded by Lea. Because of that Morgan didn't find him or Justin or Elaine because that isn't who he was looking for.

Well someone is out there, handing out summoning rituals, magic books and wolf- skin belts probably just for the hell of it to sow discord. Almost as if they were a Demi- God of discord resident in Chicago. This may be Nameless/Cowls weakness, he can’t help sowing discord even if it isn’t part of a larger scheme, like undermining the Winter Court with the Nemesis Athame, or seeking out The Word to remove the qualifier from god, or setting the White Court and White Council at each other’s throats. How many of the events in Chicago that have impinged upon Harry are due to Nameless indirectly?

I have suggested he pushed Maeve in Summer Knight towards her course of action, did he hook Marcone up with the Church Mice and then alert the Denarians just for fun? Was he behind the dogknapping of the puppies? The Circle/Black seem to have been behind it in Zoo Day. Before Changes Nameless/Cowl may have been responsible to some degree for most of Harry’s Files, some by design, some just for gun.

Nameless is an interesting character but since he didn't appear in the books prior to The Law, by WOJ he can't be Cowl. As for the major things in your first paragraph, Nemesis/Justine pretty much claims credit for these when she thinks she has Harry beaten on the boat. If Nameless had a hand in pushing Maeve, Mab would have had a "serious discussion" with him and he'd likely still be in an exit interview like Slate's. I do agree that he could have hooked Marcone up with the Church Mice but telling Nic would be against the interests of his client, so not that part. Anybody could have been behind the puppies so he's as good a guess there as any. 

So for a WAG, Mirror Justin and Elaine are Cowl and Kumori? They fled here to escape Mirror Harry's search.

I'll go you one better. We know WHEN Mab will lie. The last book is called Empty Night. A sky without stars.

That could also be a premonition of her death. She could go to her grave truthful.